What have we here?

Lichens are two organisms that operate as one, a symbiotic partnership of a fungus with a green or blue-green algae (sometimes all three).  The algae’s photosynthesis feeds the fungus.  The fungus gathers and retains water and nutrients and protects the algae.

Those that grow on trees are epiphytes, totally dependent on the surrounding air and precipitation for their nutrition.  As they take in air, their tissues absorb suspended elements in concentrations that mimic the air quality.

Lichens can thrive in some of the harshest habitats on earth but epiphytes can’t live in the presence of air pollution, so we were really surprised to find them on our Duck Hollow walk on 29 October 2019 when the air smelled of rotten eggs.

The smell is hydrogen sulfide from US Steel’s Clairton Coke Works, 8 miles away. On cold calm days the pollution creeps up the Mon Valley and blankets Pittsburgh’s East End, a reminder of Pittsburgh’s Smoky City days.

The pollution happens all too frequently, as shown in these screenshots from SmellPGH.org on 28 and 29 Oct 2019. (SmellPGH is a crowd-sourced app for reporting air pollution smells. Many dark red triangles mean the air smelled really bad that day. Click here for more info.)

We can smell hydrogen sulfide but not two dangerous air pollutants that travel with it: sulfur dioxide and particulate. Fructose lichens — the kind that stand out from the branch like those shown above — cannot survive in the presence of sulfur dioxide.

We were amazed. What have we here?

(photos by John Bauman, screenshots from SmellPGH.org; click on the captions to see the SmellPGH website)

At this time of year milkweed pods burst open and the seeds disperse, carried on the wind by sprigs of fluff.

The fluff doesn’t look aerodynamic so how does the the seed stay airborne for so long? Recent studies explaining the flight properties of dandelion fluff may provide a clue for milkweed. Let’s look at dandelions.

Each dandelion seed is attached to parachute-like bit of fluff called a pappus. They look like this before they leave on their journey.

When a seed lets loose it dangles below the pappus and floats on the breeze for seven (7) feet or several miles. The goal is for the seed to land far from the parent plant.

In experiments in 2018, published in the journal Nature, researchers at the University of Edinburgh found that each pappus creates a separated vortex ring on the downwind side that keeps the seed aloft. This video shows how it works.

Read more in Dandelion Seeds Reveal A New Form of Aerodynamics in IFLScience.

Milkweed fluff is not the same shape as dandelions’ so a different mechanism may be at work.

The secrets behind nature’s small flying objects may help us design our own.

(photos by Kate St. John except … floating dandelion seeds are from Wikimedia Commons; click on the caption to see the original.)

Last weekend my friend Debbie and I traveled to Williamsport for the annual Pennsylvania Society for Ornithology (PSO) meeting. Along the way we stopped at Black Moshannon State Park where we found these mushrooms disintegrating near the parking lot. Mushrooms are a mystery to me. An expert at the meeting told us what they were.

Shaggy mane mushrooms, also called shaggy ink cap (Coprinus comatus), are a common mushroom in lawns and waste places. Their caps begin as white cylinders, turn shaggy and bell shaped, liquefy into black ink and drip from the edges, eventually disintegrating into an inky blob.

The shaggy manes at Black Moshannon were all dripping black ink so we had no idea they went through the life stages shown in the Wikimedia photo below.

When they’re disintegrating shaggy manes look very unappetizing but according to Wikipedia they are edible when young. However they are frequently confused with a poisonous North American mushroom called the ‘vomiter’ mushroom Chlorophyllum molybdites. Enough said!

p.s. PSO‘s annual September meeting is a great opportunity to go birding in a new-to-you place in Pennsylvania. The outings are led by local birders who know the area well. I visited Montour Preserve and Ricketts Glen State Park last weekend. It was well worth the trip. Next year’s meeting will be in Lancaster County.

Goldenrod is going through its paces this month. Here are a few of the stages you’ll see in a native of Pennsylvania, Canada goldenrod (Solidago canadensis).

Buds like these may be hard to find in September because …

… Goldenrod is in full bloom.

Insects are busily fertilizing the flowers this month. By late September they’ll dry out and develop seeds.

In October the seeds are ready to blow on the wind.

(photos from Wikimedia Commons; click on the captions to see the originals)

Ragweed season officially began August 15 and runs through September. I’m not allergic to it, but those of you who are may want to know the enemy and learn how to avoid it.

First, a primer on what is NOT ragweed.

Goldenrod is not ragweed. Ragweed (Ambrosia sp. on left) is a wind-pollinated plant with green flowers on thin spikes. Goldenrod (Solidago sp. on right) is a bee-and-butterfly pollinated plant with yellow flowers in a feathery plume. Don’t worry about those yellow flowers. Goldenrod is not busy spreading pollen; it’s busy attracting bees.

Ragweed (Ambrosia genus) is a member of the Aster family native to the Americas but now spread to Europe. The most common species in Pennsylvania, common ragweed Ambrosia artemisiifolia, grows easily by the side of the road and in disturbed places. It doesn’t stand out.

Common ragweed’s female flowers are nearly hidden in the leaf axils and pollinated by the wind.

The male flowers are the ones to worry about. Perched on spikes, facing downward, and loaded with pollen, a slight tap is all it takes to release a cloud of pollen. Imagine what the wind can do!

A single plant may produce about a billion grains of pollen per season, and the pollen is transported on the wind. It causes about half of all cases of pollen-associated allergic rhinitis in North America. … Ragweed pollen can remain airborne for days and travel great distances, affecting people hundreds of miles away. It can even be carried 300 to 400 miles (640 km) out to sea

— Ragweed article, Wikipedia

It’s hard to avoid these pollen grains because they’re so pervasive, but you can be forewarned of a bad pollen day at pollen.com. On the other hand, your nose might know before the website does!

Meanwhile, don’t walk past this plant unawares. Here’s what it looks like in a weedy patch.

Know your enemy.

(photos from Wikimedia Commons; click on the captions to see the originals)

(*) Different species of goldenrod have different flower cluster shapes — it’s not always a plume. However tall goldenrod, pictured above, is the one most often called ragweed by mistake.